Platelet inhibition by aspirin 81 and 325 mg/day in men versus women without clinically apparent cardiovascular disease

Am J Cardiol. 2008 May 1;101(9):1359-63. doi: 10.1016/j.amjcard.2007.12.038. Epub 2008 Mar 17.


Compared with men, women have greater platelet aggregation before and after low-dose aspirin. It is not known whether high-dose aspirin therapy brings residual platelet aggregation in women closer to that in men. Our objective was to compare inhibition of platelet aggregation in women and men after low- and high-dose aspirin. We enrolled healthy subjects (n=106) in a trial of 14 days of aspirin 81 mg/day followed by 14 days of 325 mg/day. Platelet function was measured at baseline and after the 2 aspirin doses. Women had greater baseline platelet activation measurements. After the 2 aspirin doses, men and women had near complete suppression of platelet aggregation to arachidonic acid in whole blood and in platelet-rich plasma (PRP), the direct cyclo-oxygenase-1 pathway affected by aspirin. For indirect pathways, women had significantly greater residual platelet activation to collagen and adenosine diphosphate (ADP) in whole blood after the 2 aspirin doses and in response to collagen and ADP in PRP after aspirin 325 mg/day only. After aspirin 325 mg/day, women continued to have greater residual platelet aggregation compared with men after aspirin 81 mg/day in response to collagen (p=0.016 in whole blood, p=0.037 in PRP), ADP (p<0.001 in whole blood, p=0.012 in PRP), and epinephrine (p=0.03 in PRP). Excretion of urinary thromboxane metabolite (urinary 11-dehydrothromboxane B2) decreased after aspirin to a similar extent in men and women. In conclusion, women continue to have greater residual platelet activity after high-dose aspirin compared with men treated with a lower dose of aspirin.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aspirin / administration & dosage
  • Aspirin / pharmacology*
  • Cardiovascular Diseases / blood
  • Cardiovascular Diseases / drug therapy
  • Female
  • Hematocrit
  • Humans
  • Lipids / blood
  • Logistic Models
  • Male
  • Middle Aged
  • Platelet Aggregation / drug effects
  • Platelet Aggregation Inhibitors / administration & dosage
  • Platelet Aggregation Inhibitors / pharmacology*
  • Platelet Count
  • Platelet Function Tests
  • Sex Factors
  • Statistics, Nonparametric


  • Lipids
  • Platelet Aggregation Inhibitors
  • Aspirin